# Patent

## Title
Removal methods for high aspect ratio structures

## Abstract

Exemplary cleaning or etching methods may include flowing a fluorine-containing precursor into a remote plasma region of a semiconductor processing chamber. Methods may include forming a plasma within the remote plasma region to generate plasma effluents of the fluorine-containing precursor. The methods may also include flowing the plasma effluents into a processing region of the semiconductor processing chamber. A substrate may be positioned within the processing region, and the substrate may include a region of exposed oxide. Methods may also include providing a hydrogen-containing precursor to the processing region. The methods may further include removing at least a portion of the exposed oxide while maintaining a relative humidity within the processing region below about 50%. Subsequent to the removal, the methods may include increasing the relative humidity within the processing region to greater than or about 50%. The methods may further include removing an additional amount of the exposed oxide.

## Background
TECHNICAL FIELD
The present technology relates to semiconductor processes and equipment. More specifically, the present technology relates to cleaning or etching high-aspect-ratio structures.
BACKGROUND
Integrated circuits are made possible by processes which produce intricately patterned material layers on substrate surfaces. Producing patterned material on a substrate requires controlled methods for removal of exposed material. Chemical etching is used for a variety of purposes including transferring a pattern in photoresist into underlying layers, thinning layers, or thinning lateral dimensions of features already present on the surface. Often it is desirable to have an etch process that etches one material faster than another facilitating, for example, a pattern transfer process. Such an etch process is said to be selective to the first material. As a result of the diversity of materials, circuits, and processes, etch processes have been developed with a selectivity towards a variety of materials.
Etch processes may be termed wet or dry based on the materials used in the process. A wet HF etch preferentially removes silicon oxide over other dielectrics and materials. However, wet processes may have difficulty penetrating some constrained trenches and also may sometimes deform the remaining material. Dry etches produced in local plasmas formed within the substrate processing region can penetrate more constrained trenches and exhibit less deformation of delicate remaining structures. However, local plasmas may damage the substrate through the production of electric arcs as they discharge.
Thus, there is a need for improved systems and methods that can be used to produce high quality devices and structures. These and other needs are addressed by the present technology.
SUMMARY
Exemplary cleaning, removal, and etching methods may include flowing a fluorine-containing precursor into a remote plasma region of a semiconductor processing chamber. The methods may include forming a plasma within the remote plasma region to generate plasma effluents of the fluorine-containing precursor. The methods may also include flowing the plasma effluents into a processing region of the semiconductor processing chamber. A substrate may be positioned within the processing region, and the substrate may include a region of exposed oxide. The methods may also include providing a hydrogen-containing precursor to the processing region. The methods may further include removing at least a portion of the exposed oxide while maintaining a relative humidity within the processing region below about 50%. Subsequent to the removal, the methods may include increasing the relative humidity within the processing region to greater than or about 50%. The methods may further include removing an additional amount of the exposed oxide.
Exemplary methods may also include continuing to flow the plasma effluents into the processing region while increasing the relative humidity within the processing region. A flow rate of the plasma effluents may be reduced while increasing the relative humidity within the processing region. In embodiments, a temperature of the substrate may be reduced while increasing the relative humidity within the processing region. For example, the temperature may be reduced by at least about 5° C. In embodiments a pressure within the processing chamber may be increased while increasing the relative humidity within the processing region. For example, the pressure may be increased by at least about 1 Torr. The relative humidity may be increased above about 65% in some embodiments. After methods according to the present technology have been performed including removal of an additional amount of exposed oxide, a concentration of fluorine in the substrate may be below or about 5%. Similarly, a concentration of oxygen in the substrate may be below or about 8%. In some embodiments, the hydrogen-containing precursor may bypass the remote plasma region when provided to the processing region. In some embodiments, the processing region may be maintained plasma free during the removing operations. Additionally, the relative humidity may be increased incrementally during exemplary methods, and may be increased incrementally by less than or about 20% per increment.
The present technology also encompasses cleaning methods. The methods may include flowing a fluorine-containing precursor into a remote plasma region of a semiconductor processing chamber while forming a plasma within the remote plasma region to generate plasma effluents of the fluorine-containing precursor. The methods may include flowing the plasma effluents into a processing region of the semiconductor processing chamber. The processing region may house or contain a substrate that may include a high-aspect-ratio feature having a region of exposed oxide. While flowing the plasma effluents into the processing region, the methods may include providing a hydrogen-containing precursor to the processing region. The methods may include removing at least a portion of the exposed oxide while maintaining a relative humidity within the processing region at greater than or about 50%. The methods may further include, subsequent the removing at least a portion of the exposed oxide, increasing a flow rate of the fluorine-containing precursor while maintaining the relative humidity within the processing region at greater than or about 50%. The methods may also include removing an additional amount of the exposed oxide.
In embodiments removing an additional amount of the exposed oxide may lower a concentration of oxygen by at least about 5%. In exemplary methods, the flow rate of the fluorine-containing precursor may be increased by at least about 2 sccm. In embodiments, a thickness of the exposed region of oxide prior to the removal operations may be less than or about 2 nm. Additionally, in some embodiments, a critical dimension of the high-aspect-ratio feature may be reduced by less than or about 1%.
The present technology also encompasses removal methods. The methods may include flowing a fluorine-containing precursor into a remote plasma region of a semiconductor processing chamber while forming a plasma within the remote plasma region to generate plasma effluents of the fluorine-containing precursor. The methods may include flowing the plasma effluents into a processing region of the semiconductor processing chamber. The processing region may house a substrate, which may have one or more high-aspect-ratio features having a region of exposed oxide. While flowing the plasma effluents into the processing region, the methods may include providing a hydrogen-containing precursor to the processing region. The methods may include continuing to flow the plasma effluents and the hydrogen-containing precursor into the processing region for at least about 200 seconds. The methods may also include removing at least a portion of the exposed oxide while maintaining a relative humidity within the processing region at greater than or about 50%. In some embodiments, the removing operation may reduce a surface-level concentration of oxygen within the substrate by at least about 3%.
Such technology may provide numerous benefits over conventional systems and techniques. For example, the processes may allow high-aspect-ratio features to be etched without developing pattern collapse. Additionally, the processes may allow a material removal to be performed while limiting a surface contamination level of a substrate. These and other embodiments, along with many of their advantages and features, are described in more detail in conjunction with the below description and attached figures.



BRIEF DESCRIPTION OF THE DRAWINGS
A further understanding of the nature and advantages of the disclosed technology may be realized by reference to the remaining portions of the specification and the drawings.
FIG. 1 shows a top plan view of one embodiment of an exemplary processing system according to embodiments of the present technology.
FIG. 2A shows a schematic cross-sectional view of an exemplary processing chamber according to embodiments of the present technology.
FIG. 2B shows a detailed view of a portion of the processing chamber illustrated in FIG. 2A according to embodiments of the present technology.
FIG. 3 shows a bottom plan view of an exemplary showerhead according to embodiments of the present technology.
FIG. 4 shows exemplary operations in a method according to embodiments of the present technology.
FIGS. 5A-5C show cross-sectional views of substrates being processed according to embodiments of the present technology.
FIG. 6 shows a chart illustrating surface concentrations of elements in relation to relative humidity according to embodiments of the present technology.
FIG. 7 shows exemplary operations in a method according to embodiments of the present technology.
FIG. 8 shows a chart illustrating surface concentrations of elements in relation to precursor flow rate according to embodiments of the present technology.
FIG. 9 shows exemplary operations in a method according to embodiments of the present technology.
FIG. 10 shows a chart illustrating surface concentrations of elements in relation to elapsed time according to embodiments of the present technology.



Several of the figures are included as schematics. It is to be understood that the figures are for illustrative purposes, and are not to be considered of scale unless specifically stated to be of scale. Additionally, as schematics, the figures are provided to aid comprehension and may not include all aspects or information compared to realistic representations, and may include additional or exaggerated material for illustrative purposes.
In the appended figures, similar components and/or features may have the same reference label. Further, various components of the same type may be distinguished by following the reference label by a letter that distinguishes among the similar components. If only the first reference label is used in the specification, the description is applicable to any one of the similar components having the same first reference label irrespective of the letter.
DETAILED DESCRIPTION
Diluted acids may be used in many different semiconductor processes for cleaning substrates, and removing materials from those substrates. For example, diluted hydrofluoric acid can be an effective etchant for silicon oxide, and may be used to remove silicon oxide from silicon surfaces. After the etching or cleaning operation is complete, the acid may be dried from the wafer or substrate surface. Using dilute hydrofluoric acid (“DHF”) may be termed a “wet” etch, and the diluent is often water. Water has a relatively high surface tension that may act on the surfaces with which it is in contact.
Device patterning and features that continue to shrink in dimension may include delicate features etched or formed on a substrate. For example, many processing operations may work upon or form trenches, holes, or other features in a substrate or materials on a substrate. The aspect ratio, defined as the height to width ratio, may be very high in devices, and can be on the order of 5, 10, 20, 50, 100 or greater. Many of these features may have not only high aspect ratios, but also reduced dimensions on the scale of a few nanometers, for example, such that the critical dimensions across the substrate—often the width or dimension of these features—may be less than 10 nm, less than 5 nm, less than 3 nm, less than 2 nm, less than 1 nm, or even smaller. For example, the width of any particular column or wall between two trenches may be of only a few nanometers. The thinner is this material, the more impact stresses may pose on the integrity of the structure. Additionally, the material composing the structure may also impact the effect of exerted pressures or stresses on the material, be it a substrate material, dielectric, photo-resist, etc.
Issues may arise when delicate, high-aspect-ratio features are cleaned, etched, or processed, because the fluids may exhibit surface tensions that may be much higher than can be managed by the features. In designs having multiple features, layers, or materials, even a small amount of feature deformation or collapse can cause short circuits through the produced device rendering it inoperable. For example, although DHF may work well on low aspect ratio structures, when used as an etchant on high-aspect-ratio features, when the etching operation is finished and the DHF is dried or removed, the surface tension imposed on the features during the drying may cause pattern collapse. As device features continue to shrink, wet etching may no longer be sufficient because of its effect on high-aspect-ratio features. One promising technology for fluid removal in cleaning operations is by performing drying operations with super-critical fluids. Although these techniques may provide surfaces that are drier and less prone to pattern collapse, the amount of preparation, hardware requirements, and the number of operations involved may reduce the efficiency of overall substrate processing.
The present technology overcomes these issues by performing a dry etch process that provides adequate selectivity for the removal of silicon oxide relative to silicon, while maintaining high-aspect-ratio structures. The technology utilizes plasma enhanced precursors, which may include fluorine-containing precursors, to remove exposed regions of silicon oxide from silicon surfaces. By utilizing non-liquid materials, the effect on substrate features may be minimized. The term “dry” with respect to etching may be utilized to mean that liquid water may not be used in the operations, unlike with wet etches in which water may be used as a diluent or component, such as with DHF.
Although the remaining disclosure will routinely identify specific etching processes utilizing the disclosed technology, it will be readily understood that the systems and methods are equally applicable to deposition and cleaning processes as may occur in the described chambers. Accordingly, the technology should not be considered to be so limited as for use with etching processes or chambers alone. Moreover, although an exemplary chamber is described to provide foundation for the present technology, it is to be understood that the present technology can be applied to virtually any semiconductor processing chamber that may allow the operations described.
FIG. 1 shows a top plan view of one embodiment of a processing system 100 of deposition, etching, baking, and curing chambers according to embodiments. In the figure, a pair of front opening unified pods (FOUPs) 102 supply substrates of a variety of sizes that are received by robotic arms 104 and placed into a low pressure holding area 106 before being placed into one of the substrate processing chambers 108a-f, positioned in tandem sections 109a-c. A second robotic arm 110 may be used to transport the substrate wafers from the holding area 106 to the substrate processing chambers 108a-f and back. Each substrate processing chamber 108a-f, can be outfitted to perform a number of substrate processing operations including the dry etch processes described herein in addition to cyclical layer deposition (CLD), atomic layer deposition (ALD), chemical vapor deposition (CVD), physical vapor deposition (PVD), etch, pre-clean, degas, orientation, and other substrate processes.
The substrate processing chambers 108a-f may include one or more system components for depositing, annealing, curing and/or etching a dielectric film on the substrate wafer. In one configuration, two pairs of the processing chambers, e.g., 108c-d and 108e-f, may be used to deposit dielectric material on the substrate, and the third pair of processing chambers, e.g., 108a-b, may be used to etch the deposited dielectric. In another configuration, all three pairs of chambers, e.g., 108a-f, may be configured to etch a dielectric film on the substrate. Any one or more of the processes described may be carried out in chamber(s) separated from the fabrication system shown in different embodiments. It will be appreciated that additional configurations of deposition, etching, annealing, and curing chambers for dielectric films are contemplated by system 100.
FIG. 2A shows a cross-sectional view of an exemplary process chamber system 200 with partitioned plasma generation regions within the processing chamber. During film etching, e.g., titanium nitride, tantalum nitride, tungsten, silicon, polysilicon, silicon oxide, silicon nitride, silicon oxynitride, silicon oxycarbide, etc., a process gas may be flowed into the first plasma region 215 through a gas inlet assembly 205. A remote plasma system (RPS) 201 may optionally be included in the system, and may process a first gas which then travels through gas inlet assembly 205. The inlet assembly 205 may include two or more distinct gas supply channels where the second channel (not shown) may bypass the RPS 201, if included.
A cooling plate 203, faceplate 217, ion suppressor 223, showerhead 225, and a substrate support 265, having a substrate 255 disposed thereon, are shown and may each be included according to embodiments. The pedestal 265 may have a heat exchange channel through which a heat exchange fluid flows to control the temperature of the substrate, which may be operated to heat and/or cool the substrate or wafer during processing operations. The wafer support platter of the pedestal 265, which may comprise aluminum, ceramic, or a combination thereof, may also be resistively heated in order to achieve relatively high temperatures, such as from up to or about 100° C. to above or about 1100° C., using an embedded resistive heater element.
The faceplate 217 may be pyramidal, conical, or of another similar structure with a narrow top portion expanding to a wide bottom portion. The faceplate 217 may additionally be flat as shown and include a plurality of through-channels used to distribute process gases. Plasma generating gases and/or plasma excited species, depending on use of the RPS 201, may pass through a plurality of holes, shown in FIG. 2B, in faceplate 217 for a more uniform delivery into the first plasma region 215.
Exemplary configurations may include having the gas inlet assembly 205 open into a gas supply region 258 partitioned from the first plasma region 215 by faceplate 217 so that the gases/species flow through the holes in the faceplate 217 into the first plasma region 215. Structural and operational features may be selected to prevent significant backflow of plasma from the first plasma region 215 back into the supply region 258, gas inlet assembly 205, and fluid supply system 210. The faceplate 217, or a conductive top portion of the chamber, and showerhead 225 are shown with an insulating ring 220 located between the features, which allows an AC potential to be applied to the faceplate 217 relative to showerhead 225 and/or ion suppressor 223. The insulating ring 220 may be positioned between the faceplate 217 and the showerhead 225 and/or ion suppressor 223 enabling a capacitively coupled plasma (CCP) to be formed in the first plasma region. A baffle (not shown) may additionally be located in the first plasma region 215, or otherwise coupled with gas inlet assembly 205, to affect the flow of fluid into the region through gas inlet assembly 205.
The ion suppressor 223 may comprise a plate or other geometry that defines a plurality of apertures throughout the structure that are configured to suppress the migration of ionically-charged species out of the first plasma region 215 while allowing uncharged neutral or radical species to pass through the ion suppressor 223 into an activated gas delivery region between the suppressor and the showerhead. In embodiments, the ion suppressor 223 may comprise a perforated plate with a variety of aperture configurations. These uncharged species may include highly reactive species that are transported with less reactive carrier gas through the apertures. As noted above, the migration of ionic species through the holes may be reduced, and in some instances completely suppressed. Controlling the amount of ionic species passing through the ion suppressor 223 may advantageously provide increased control over the gas mixture brought into contact with the underlying wafer substrate, which in turn may increase control of the deposition and/or etch characteristics of the gas mixture. For example, adjustments in the ion concentration of the gas mixture can significantly alter its etch selectivity, e.g., SiNx:SiOx etch ratios, Si:SiOx etch ratios, etc. In alternative embodiments in which deposition is performed, it can also shift the balance of conformal-to-flowable style depositions for dielectric materials.
The plurality of apertures in the ion suppressor 223 may be configured to control the passage of the activated gas, i.e., the ionic, radical, and/or neutral species, through the ion suppressor 223. For example, the aspect ratio of the holes, or the hole diameter to length, and/or the geometry of the holes may be controlled so that the flow of ionically-charged species in the activated gas passing through the ion suppressor 223 is reduced. The holes in the ion suppressor 223 may include a tapered portion that faces the plasma excitation region 215, and a cylindrical portion that faces the showerhead 225. The cylindrical portion may be shaped and dimensioned to control the flow of ionic species passing to the showerhead 225. An adjustable electrical bias may also be applied to the ion suppressor 223 as an additional means to control the flow of ionic species through the suppressor.
The ion suppressor 223 may function to reduce or eliminate the amount of ionically charged species traveling from the plasma generation region to the substrate. Uncharged neutral and radical species may still pass through the openings in the ion suppressor to react with the substrate. It should be noted that the complete elimination of ionically charged species in the reaction region surrounding the substrate may not be performed in embodiments. In certain instances, ionic species are intended to reach the substrate in order to perform the etch and/or deposition process. In these instances, the ion suppressor may help to control the concentration of ionic species in the reaction region at a level that assists the process.
Showerhead 225 in combination with ion suppressor 223 may allow a plasma present in first plasma region 215 to avoid directly exciting gases in substrate processing region 233, while still allowing excited species to travel from chamber plasma region 215 into substrate processing region 233. In this way, the chamber may be configured to prevent the plasma from contacting a substrate 255 being etched. This may advantageously protect a variety of intricate structures and films patterned on the substrate, which may be damaged, dislocated, or otherwise warped if directly contacted by a generated plasma. Additionally, when plasma is allowed to contact the substrate or approach the substrate level, the rate at which oxide species etch may increase. Accordingly, if an exposed region of material is oxide, this material may be further protected by maintaining the plasma remotely from the substrate.
The processing system may further include a power supply 240 electrically coupled with the processing chamber to provide electric power to the faceplate 217, ion suppressor 223, showerhead 225, and/or pedestal 265 to generate a plasma in the first plasma region 215 or processing region 233. The power supply may be configured to deliver an adjustable amount of power to the chamber depending on the process performed. Such a configuration may allow for a tunable plasma to be used in the processes being performed. Unlike a remote plasma unit, which is often presented with on or off functionality, a tunable plasma may be configured to deliver a specific amount of power to the plasma region 215. This in turn may allow development of particular plasma characteristics such that precursors may be dissociated in specific ways to enhance the etching profiles produced by these precursors.
A plasma may be ignited either in chamber plasma region 215 above showerhead 225 or substrate processing region 233 below showerhead 225. Plasma may be present in chamber plasma region 215 to produce the radical precursors from an inflow of, for example, a fluorine-containing precursor or other precursor. An AC voltage typically in the radio frequency (RF) range may be applied between the conductive top portion of the processing chamber, such as faceplate 217, and showerhead 225 and/or ion suppressor 223 to ignite a plasma in chamber plasma region 215 during deposition. An RF power supply may generate a high RF frequency of 13.56 MHz but may also generate other frequencies alone or in combination with the 13.56 MHz frequency.
FIG. 2B shows a detailed view 253 of the features affecting the processing gas distribution through faceplate 217. As shown in FIGS. 2A and 2B, faceplate 217, cooling plate 203, and gas inlet assembly 205 intersect to define a gas supply region 258 into which process gases may be delivered from gas inlet 205. The gases may fill the gas supply region 258 and flow to first plasma region 215 through apertures 259 in faceplate 217. The apertures 259 may be configured to direct flow in a substantially unidirectional manner such that process gases may flow into processing region 233, but may be partially or fully prevented from backflow into the gas supply region 258 after traversing the faceplate 217.
The gas distribution assemblies such as showerhead 225 for use in the processing chamber section 200 may be referred to as dual channel showerheads (DCSH) and are additionally detailed in the embodiments described in FIG. 3. The dual channel showerhead may provide for etching processes that allow for separation of etchants outside of the processing region 233 to provide limited interaction with chamber components and each other prior to being delivered into the processing region.
The showerhead 225 may comprise an upper plate 214 and a lower plate 216. The plates may be coupled with one another to define a volume 218 between the plates. The coupling of the plates may be so as to provide first fluid channels 219 through the upper and lower plates, and second fluid channels 221 through the lower plate 216. The formed channels may be configured to provide fluid access from the volume 218 through the lower plate 216 via second fluid channels 221 alone, and the first fluid channels 219 may be fluidly isolated from the volume 218 between the plates and the second fluid channels 221. The volume 218 may be fluidly accessible through a side of the gas distribution assembly 225.
FIG. 3 is a bottom view of a showerhead 325 for use with a processing chamber according to embodiments. Showerhead 325 may correspond with the showerhead 225 shown in FIG. 2A. Through-holes 365, which show a view of first fluid channels 219, may have a plurality of shapes and configurations in order to control and affect the flow of precursors through the showerhead 225. Small holes 375, which show a view of second fluid channels 221, may be distributed substantially evenly over the surface of the showerhead, even amongst the through-holes 365, and may help to provide more even mixing of the precursors as they exit the showerhead than other configurations.
The chambers discussed previously may be used in performing exemplary methods including etching methods. Turning to FIG. 4 is shown exemplary operations in a method 400 according to embodiments of the present technology. Prior to the first operation of the method a substrate may be processed in one or more ways before being placed within a processing region of a chamber in which method 400 may be performed. For example, trenches, holes, or other features may be formed in a substrate, which may include a silicon substrate. In some embodiments the holes may be formed by reactive-ion etching, which may utilize an oxide hardmask. Reactive-ion etching may produce deep, high-aspect-ratio structures, but may leave residue within the formed structure, that may include carbon, oxygen, or other materials. Ashing operations may be performed, although oxide residue materials may still remain in the formed structures. Some or all of these operations may be performed in chambers or system tools as previously described, or may be performed in different chambers on the same system tool, which may include the chamber in which the operations of method 400 are performed.
The method 400 may include flowing a fluorine-containing precursor into a remote plasma region of a semiconductor processing chamber at operation 405. An exemplary chamber may be chamber 200 previously described, which may include one or both of the RPS unit 201 or first plasma region 215. Either or both of these regions may be the remote plasma region used in operation 405. A plasma may be generated within the remote plasma region at operation 410, which may generate plasma effluents of the fluorine-containing precursor. The plasma effluents may be flowed to a processing region of the chamber at operation 415. The plasma effluents may interact with the substrate in the processing region, which may include a trench or other feature formed through a semiconductor substrate, which may include silicon, germanium, or any other substrate or combination of elements as would be understood.
The substrate may include a region of exposed oxygen, which may be from one or more sources. For example, the oxygen may be an oxygen hardmask that remains after trenches or other features have been formed. The oxide may also be or include a layer of oxide that has formed from exposure of the substrate to air. For example, when a silicon substrate is exposed to air or some other oxygen source, a thin layer of oxide may form on the substrate. At operation 420, a hydrogen-containing precursor may be provided to the processing region along with the plasma effluents. The plasma effluents and hydrogen-containing precursor may interact with the exposed oxide to remove at least a portion of the exposed oxide at operation 425. During the removal, the relative humidity within the processing region may be maintained below or about 50%.
After a portion of the oxide has been removed at operation 425, the relative humidity within the processing region may be increased to greater than or about 50% at operation 430. While increasing the relative humidity, the plasma effluents may be continued to be flowed into the processing region in some embodiments. An additional amount of the exposed oxide may then be removed at operation 435. By increasing the relative humidity within the processing region during the removal, an additional amount of oxide may be removed that may allow additional benefits of the process that will be described further below.
Precursors used in the method may include a fluorine-containing precursor or a halogen-containing precursor. An exemplary fluorine-containing precursor may be nitrogen trifluoride (NF3), which may be flowed into the remote plasma region, which may be separate from, but fluidly coupled with, the processing region. Other sources of fluorine may be used in conjunction with or as replacements for the nitrogen trifluoride. In general, a fluorine-containing precursor may be flowed into the remote plasma region and the fluorine-containing precursor may include at least one precursor selected from the group of atomic fluorine, diatomic fluorine, nitrogen trifluoride, carbon tetrafluoride, hydrogen fluoride, xenon difluoride, and various other fluorine-containing precursors used or useful in semiconductor processing. The precursors may also include any number of carrier gases, which may include nitrogen, helium, argon, or other noble, inert, or useful precursors.
The hydrogen-containing precursor may include hydrogen, a hydrocarbon, water, hydrogen peroxide, or other materials that may include hydrogen as would be understood by the skilled artisan. Additional precursors such as carrier gases or inert materials may be included with the secondary precursors as well. One or more of the precursors may bypass the remote plasma region and be flowed into additional regions of the processing chamber. These precursors may be mixed with the plasma effluents in the processing region or some other region of the chamber. For example, while the fluorine-containing precursor is flowed through the remote plasma region to produce fluorine-containing plasma effluents, the hydrogen-containing precursor may bypass the remote plasma region. The hydrogen-containing precursor may bypass the remote plasma region by a bypass at a top of the chamber, or may be flowed into a separate region of the chamber, such as through a port providing access to the volume within the showerhead, such as showerhead 225 of FIG. 2. The hydrogen-containing precursor may then flow into the processing region, where it may then mix or interact with fluorine-containing plasma effluents. In embodiments, the plasma processing region may be maintained plasma free during the removal operations. By plasma free, is meant that plasma may not be actively formed within the processing region during the operations, although plasma effluents produced remotely as described earlier, may be used during the operations.
Additional aspects of the present technology may be further understood with reference to FIGS. 5A-5C. FIG. 5 shows cross-sectional views of substrates being processed according to embodiments of the present technology. Beginning with FIG. 5A is shown a cross-sectional view of a substrate on which the present technology may be utilized. For example, a silicon substrate 505 may have one or more features formed or defined within its surface, such as trench 510 as illustrated. In embodiments encompassed by the present technology, the trench 510 may be formed by a reactive-ion etching process, although other etching processes that may form trenches and other features are similarly encompassed. The trench 510 may be a high-aspect-ratio trench as previously discussed, and may have an aspect ratio greater than 10, greater than 50, greater than 100, or within any of these numbers or others as deeper, narrower trenches may be formed.
In the exemplary situation in which reactive-ion etching may have been used to form trench 510, an oxide hardmask 515 may be formed on a surface of the substrate 505. Additionally, residue material 520 may be formed or left within the trench 510, which may include carbon, oxygen, or other impurities from the etching. Operations of a process, such as selected operations of process 400 described previously, may be performed to remove the exposed oxide material from the surface of the silicon substrate 505. For example, a hydrogen-containing precursor and plasma effluents of a fluorine-containing precursor may be delivered to the processing region to at least partially remove the oxide hardmask 515 as well as the residue material 520. Because the trench 510 along with any other features may have high aspect ratios, the relative humidity within the processing region may be maintained below about 50% in embodiments. By maintaining the relative humidity below about 50%, water droplets may not form along the surfaces, which may cause pattern deformation or collapse when they are dried or removed.
After the oxide hardmask 515 and the residue material 520 have been removed, there may be a thin film of oxide remaining. As illustrated in FIG. 5B, oxide material 525 may be present on substrate 505. For example, oxide material 525 may be an oxide layer present across the silicon surface from exposure to air, or may be a remaining portion of oxide hardmask 515. The oxide material 525 may be a thin layer of oxide that may be less than or about 10 nm, less than or about 8 nm, less than or about 6 nm, less than or about 5 nm, less than or about 4 nm, less than or about 3 nm, less than or about 2 nm, less than or about 1 nm, or less. Dry etching operations, such as discussed with relation to FIG. 4, may have difficulty in removing the oxide material 525. For example, the remaining oxide material 525 may be slightly more amorphous at the interface between the silicon substrate 505 and the overlying oxide material 525. The final atomic layers of oxygen may be shared between the silicon matrix and with the silicon oxide structure. In some cases, dry etching operations may be incapable of cleaving these bonds, which may allow residual oxygen to remain at the surface, such as with oxide material 525.
Dry etching operations that may include certain operations as described with respect to FIG. 4, may increase fluorine concentration at a surface level of the substrate. When the dry etching fails to cleave the final layers of oxygen from the silicon surface, fluorine used in the etchant may bond or associate with the oxide material 525. When used for lower-aspect-ratio features, wet etches may not retain within the substrate the amount of fluorine as the dry etches, but the wet etches may be incapable of maintaining high-aspect-ratio features, and may cause pattern collapse due to surface tension. The residual fluorine may act as impurities that effect device function. For example, the trenches or features may, for example, be formed in the fabrication of memory devices. Before the cells are formed, a relatively or substantially pure substrate surface may be sought. Impurities may increase leakage current from the device, which may in turn increase power consumption, and reduce battery life due the increased refresh rate to maintain memory data from the leakage.
Oxide material 525 may allow a surface-level concentration of fluorine within the substrate to increase. The fluorine contained within or attached to the oxide material 525 may be up to or greater than an atomic percent of 8% in certain regions of the substrate, such as a center region. A desired level of fluorine to minimize leakage current from this impurity may be below or about 3%, for example. Such a level of fluorine incorporation may be produced by wet etching, but as feature size is reduced, wet etching may cause pattern collapse and device failure. The present technology, however, may utilize relative humidity and/or one or more other conditions discussed below to reduce the surface-level concentration of fluorine below other dry etch processes.
As described previously with FIG. 4, the relative humidity within the processing chamber may be increased above about 50%. By increasing the relative humidity, additional oxygen material may be removed from the silicon surface, which may remove residual fluorine that may be associated with the oxygen. By reducing the atomic percentage of fluorine, leakage current may be reduced, and device performance may be improved. However, the inventors have additionally determined that the operations may be performed in a series of operations that first removes a bulk portion of oxide material before the relative humidity is increased. If the relative humidity is increased above 50% initially, certain issues may occur. At high enough relative humidity, water droplets may be formed on the surface of the substrate, which may then cause pattern collapse or deformation as previously explained. Even a monolayer of liquid water has been shown to produce pattern deformation or collapse.
Additionally, the oxide hardmask during removal with a dry etchant may produce silicon fluoride. With water, however, fluorosilicic acid may be produced from the oxide hardmask which may cause pattern collapse due to a relatively tacky consistency. Accordingly, when an oxide hardmask is being removed, the operations may be performed at lower relative humidity, such as about 25% relative humidity, for example, to remove the majority of the hardmask material. In other embodiments, the relative humidity may be maintained below or about 50%, below or about 45%, below or about 40%, below or about 35%, below or about 30%, below or about 25%, below or about 20% below or about 15%, below or about 10%, or lower. The relative humidity may also be maintained between any of these numbers, or at any smaller range included within these ranges.
When the remaining oxide material has been reduced sufficiently, such as below a threshold of a few nanometers or less, or when the etching operation may not remove additional oxide material, the relative humidity may be increased above about 50%. The increased relative humidity may allow additional oxygen to be removed, and allow fluorine that may be associated or attached to the oxide to me removed as well. The relative humidity may be increased above or about 50% in embodiments, and may also be increased above or about 55%, above or about 60% above or about 65%, above or about 70%, above or about 75%, above or about 80%, above or about 85%, above or about 90%, above or about 95%, or higher, although at 100% relative humidity liquid water may be present, which may cause pattern collapse or deformation. Accordingly, the relative humidity may be maintained below or about 100%, between any of the other stated percentages, or within any smaller range within the stated ranges.
As illustrated in FIG. 5C, the increased relative humidity may allow additional oxide material 525 to be removed from substrate 505, which may allow the removal of incorporated fluorine. The present technology may similarly be used to remove thin layers of oxygen or oxide that may be on a substrate, such as from air exposure, without the operations for removing the hardmask material. For example, a substantially clean substrate that may have been exposed to air may have certain operations of method 400 performed to further clean the substrate prior to additional processing, such as beginning with a substrate similar to that illustrated in FIG. 5B.
Turning to FIG. 6 is shown a chart illustrating surface concentrations of elements in relation to relative humidity according to embodiments of the present technology. The chart illustrates selected operations of method 400 that are performed with increasing humidity. For example, a substrate, such as a silicon substrate, may have a thin layer of oxide material, such as layer 525 illustrated in FIG. 5B. A hydrogen-containing precursor, such as water vapor, may be delivered to a processing region of a semiconductor processing chamber along with plasma effluents of a fluorine-containing precursor. FIG. 6 shows diamonds 605, which correspond to the concentration of fluorine within the silicon substrate, such as within the residual oxide material at the surface of the substrate. FIG. 6 also include squares 610, which correspond to the concentration of oxygen within the silicon substrate, such as at the surface-level oxide material. As illustrated in FIG. 6, removal operations may not completely remove the oxide material. Triangles 615 illustrate the actual thickness of the residual oxide material on a surface of the substrate. As illustrated, the thickness may be less than 1 nm after hardmask removal, such as about 6 Å.
FIG. 6 also illustrates that as relative humidity is increased above 25%, the fluorine concentration slightly reduces, while the oxygen concentration and oxide thickness are substantially maintained. However, a step-wise change occurs as the relative humidity is increased above about 50% relative humidity, and the oxygen concentration, oxide thickness, and fluorine concentration are all reduced. The fluorine concentration may be reduced below about 2%, which may provide adequate device quality and leakage effects. Accordingly, FIG. 6 illustrates how the present technology utilizes increased relative humidity to reduce fluorine concentration within a substrate, while maintaining features on the surface. The devices used to produce FIG. 6 maintained critical dimensions across the substrate, for example the high-aspect-ratio features were not substantially reduced, and pattern deformation or collapse did not occur across the substrate. In embodiments, the critical dimensions of the substrate, such as or including high-aspect-ratio feature widths, may be reduced by less than 10% in embodiments, and may be reduced by less than or about 8%, less than or about 6%, less than or about 5%, less than or about 4%, less than or about 3%, less than or about 2%, less than or about 1%, or may be substantially or essentially maintained by the present technology.
Process conditions may also impact the operations performed in method 400 as well as other removal methods according to the present technology. Each of the operations of method 400 may be performed during a constant temperature in embodiments, while in some embodiments the temperature may be adjusted during different operations. For example, the substrate, pedestal, or chamber temperature during the method 400 may be maintained below or about 50° C. in embodiments. The substrate temperature may also be maintained below or about 45° C., below or about 40° C., below or about 35° C., below or about 30° C., below or about 25° C., below or about 20° C., below or about 15° C., below or about 10° C., below or about 5° C., below or about 0° C., below or about −5° C., or lower. In some embodiments, however, the temperature may be maintained above or about 0° C. to prevent the hydrogen-containing precursor, which may be water, from freezing. The temperature may also be maintained at any temperature within these ranges, within smaller ranges encompassed by these ranges, or between any of these ranges.
In some embodiments the first removal operation 425 may be performed at a first temperature, while the additional removal operation 435 may be performed at a second temperature. Either or both of the temperatures may be within any of the ranges previously described. The second temperature may be lower than the first temperature in embodiments. For example, during the relative humidity increase, the temperature of the substrate may be lowered from the first temperature to the second temperature. By lowering the temperature of the substrate, the relative humidity at the wafer level may also be increased without adding substantially more water vapor to the processing chamber. The opportunity for water droplets to form on the chamber components or on the substrate may then be reduced, which may aid in reducing or preventing pattern deformation or collapse.
For example, the first temperature may be greater than or about 10° C., and the second temperature may be less than or about 10° C. in embodiments. In some embodiments, the first temperature may be between about 10° C. and about 20° C., between about 11° C. and about 18° C., between about 12° C. and about 15° C., or may be about 12° C., about 13° C., about 14° C., or about 15° C. in embodiments. Additionally, in embodiments the second temperature may be between about 0° C. and about 10° C., between about 1° C. and about 8° C., between about 2° C. and about 5° C., or may be about 2° C., about 3° C., about 4° C., or about 5° C. in embodiments. The temperature reduction between the first temperature and the second temperature may be at least about 2° C. in embodiments, and may be at least or about 3° C., at least or about 4° C., at least or about 5° C., at least or about 6° C., at least or about 7° C., at least or about 8° C., at least or about 9° C., at least or about 10° C., at least or about 11° C., at least or about 12° C., or more. Additionally, the temperature decrease may be less than or about 15° C., or any smaller range between any of these ranges or within any of these ranges.
The pressure within the chamber may also affect the operations performed, and in embodiments the chamber pressure may be maintained below about 50 Torr, below or about 40 Torr, below or about 30 Torr, below or about 25 Torr, below or about 20 Torr, below or about 15 Torr, below or about 10 Torr, below or about 5 Torr, below or about 1 Torr, or less. The pressure may also be maintained at any pressure within these ranges, within smaller ranges encompassed by these ranges, or between any of these ranges.
In some embodiments the first removal operation 425 may be performed at a first pressure, while the additional removal operation 435 may be performed at a second pressure. Either or both of the pressures may be within any of the ranges previously described. The second pressure may be higher than the first pressure in embodiments. For example, during the relative humidity increase, the pressure within the processing chamber may be increased from the first pressure to the second pressure. By increasing the pressure within the chamber, the relative humidity at the wafer level may also be increased without adding substantially more water vapor to the processing chamber. The opportunity for water droplets to form on the chamber components or on the substrate may then be reduced, which again may aid in reducing or preventing pattern deformation or collapse.
For example, the first pressure may be less than or about 10 Torr, and the second pressure may be greater than or about 10 Torr in embodiments. In some embodiments, the first pressure may be between about 0 Torr and about 10 Torr, between about 3 Torr and about 9 Torr, between about 5 Torr and about 8 Torr, or may be about 5 Torr, about 6 Torr, about 7 Torr, or about 8 Torr in embodiments. In embodiments, the second pressure may be between about 10 Torr and about 20 Torr, between about 10 Torr and about 18 Torr, between about 11 Torr and about 15 Torr, or may be about 11 Torr, about 12 Torr, about 13 Torr, about 14 Torr, or about 15 Torr. The pressure increase between the first pressure and the second pressure may be at least about 1 Torr in embodiments, and may be at least or about 2 Torr, at least or about 3 Torr, at least or about 4 Torr, at least or about 5 Torr, at least or about 6 Torr, at least or about 7 Torr, at least or about 8 Torr, or more in embodiments. The pressure increase may be less than or about 10 Torr in embodiments, or may be a smaller range within any of these ranges or between any of these ranges.
The flow rates of one or more of the precursors may also be adjusted with any of the other processing conditions. For example, a flow rate of the fluorine-containing precursor may be reduced while increasing the relative humidity within the processing region, although in some embodiments it may be maintained or increased. During any of the operations of method 400, the flow rate of the fluorine-containing precursor may be between about 2 sccm and about 100 sccm. Additionally, the flow rate of the fluorine-containing precursor may be at least or about 2 sccm, at least or about 3 sccm, at least or about 4 sccm, at least or about 5 sccm, at least or about 6 sccm, at least or about 7 sccm, at least or about 8 sccm, at least or about 9 sccm, at least or about 10 sccm, at least or about 11 sccm, at least or about 12 sccm, at least or about 13 sccm, at least or about 14 sccm, at least or about 15 sccm, at least or about 16 sccm, at least or about 17 sccm, at least or about 18 sccm, at least or about 19 sccm, at least or about 20 sccm, at least or about 25 sccm, at least or about 30 sccm, at least or about 40 sccm, at least or about 50 sccm, at least or about 60 sccm, at least or about 80 sccm, or more. The flow rate may also be between any of these stated flow rates, or within smaller ranges encompassed by any of these numbers.
The hydrogen-containing precursor may be flowed at any of these flow rates depending on the precursor used, which may be any number of hydrogen-containing precursors. For example, if water vapor is utilized, the water may be introduced at a rate of at least or about 1 g/min. The water may also be introduced at a rate of at least or about 2 g/min, at least or about 3 g/min, at least or about 4 g/min, at least or about 5 g/min, at least or about 6 g/min, at least or about 7 g/min, at least or about 8 g/min, at least or about 9 g/min, or more, although the water may be introduced below about 10 g/min to reduce water condensation on components and the substrate. The water may also be introduced at a flow rate between any of these stated flow rates, or within smaller ranges encompassed by any of these numbers.
At the completion of method 400, a concentration of fluorine in the substrate may be below or about 8% in embodiments, and may be below or about 7%, below or about 6%, below or about 5%, below or about 4%, below or about 3%, below or about 2%, below or about 1%, or less. Similarly, a concentration of oxygen in the substrate may be below or about 15% in embodiments, and may be below or about 12%, below or about 10%, below or about 9%, below or about 8%, below or about 7%, below or about 6%, below or about 5%, below or about 4%, below or about 3%, below or about 2%, below or about 1%, or less.
The increase in relative humidity may be performed incrementally in some embodiments. For example, the relative humidity may be increased a certain percentage while the precursors are delivered to the processing region. The relative humidity may be increased in one or more increments that may be less than or about 50% relative humidity, less than or about 40% relative humidity, less than or about 30% relative humidity, less than or about 20% relative humidity, less than or about 15% relative humidity, less than or about 10% relative humidity, less than or about 5% relative humidity, or less. The relative humidity may also be increased in increments between any of these values or within smaller ranges encompassed by any of these ranges. Additionally, the relative humidity may be gradually increased from a starting relative humidity to a final relative humidity in embodiments that may be performed over a period of time to reduce the opportunity for excessive water condensation to occur, which may lead to pattern deformation or collapse.
Turning to FIG. 7 is shown exemplary operations in a method 700 according to embodiments of the present technology. Method 700 may include some or all of the operations, conditions, parameters, or results of method 400 described previously. For example, method 700 may include flowing a fluorine-containing precursor into a remote plasma region of a semiconductor processing chamber at operation 705. The precursor may be flowed while forming a plasma within the remote plasma region to generate plasma effluents of the fluorine-containing precursor. The plasma effluents may be flowed into a processing region of the chamber at operation 710. A substrate may be housed within the processing region, and the substrate may be characterized by a high-aspect-ratio feature having a region of exposed oxide.
While the plasma effluents are being flowed into the processing region, a hydrogen-containing precursor may be flowed into the processing region at operation 715. The hydrogen-containing precursor may bypass the remote plasma region in embodiments. At operation 720 at least a portion of the exposed oxide may be removed while maintaining a relative humidity within the processing region at greater than or about 50%. At operation 725, subsequent the at least partial removal, a flow rate of the fluorine-containing precursor may be increased while maintaining the relative humidity within the processing region at greater than or about 50%. Additional exposed oxide may be removed at operation 730.
The present technology may also be effective at producing the benefits described previously in conditions where the relative humidity may not be capable of increase above a threshold value. Additionally, in conjunction with the increase in relative humidity, the flow rate of the fluorine-containing precursor may be increased, which may further remove additional oxygen or fluorine materials. The method may include a threshold relative humidity value, such as at least about 50% relative humidity in order to provide the removal of materials as previously described. When the relative humidity is reduced below or about 50% for a residual oxide layer, bonds may be more difficult or incapable of cleaving as discussed above.
FIG. 8 shows a chart illustrating surface concentrations of elements in relation to precursor flow rate according to embodiments of the present technology. The chart illustrates the effect on the incorporation of oxygen and fluorine in a silicon substrate during operations of the present technology in which the fluorine-containing precursor flow rate was increased. The relative humidity during the operations was maintained between about 50% and about 65%. As illustrated, the fluorine concentration was maintained below about 3% incorporation while the fluorine-containing precursor flow rate was increased, as illustrated by squares 805. As the flow rate was increased, the thickness of the oxide layer previously discussed was reduced in thickness by over one Angstrom as illustrated by triangles 815. Additionally, the oxygen incorporation, as illustrated by diamonds 810, was reduced with increasing flow rate. The flow rate of the fluorine-containing precursor may be any of the precursor flow rates previously discussed both before and after the increase. In embodiments, the flow rate may be increased at least or about 1 sccm, at least or about 2 sccm, at least or about 3 sccm, at least or about 4 sccm, at least or about 5 sccm, at least or about 6 sccm, at least or about 7 sccm, at least or about 8 sccm, at least or about 9 sccm, at least or about 10 sccm, at least or about 11 sccm, at least or about 12 sccm, at least or about 13 sccm, at least or about 14 sccm, at least or about 15 sccm, at least or about 20 sccm, or more.
The removal operations may reduce the oxygen incorporation below about 14% in embodiments, and may lower the oxygen incorporation below or about 12%, below or about 10%, below or about 7%, below or about 6%, below or about 5%, below or about 4%, below or about 3%, below or about 2%, or less. The removal operations may also reduce the oxygen incorporation by at least or about 2%, and may reduce the oxygen incorporation by at least or about 3%, at least or about 4%, at least or about 5%, at least or about 6%, at least or about 7%, at least or about 8%, at least or about 9%, at least or about 10%, at least or about 11%, at least or about 12%, or more.
Method 700 may be performed on an oxide material, such as oxide material 525 as illustrated in FIG. 5B. The exposed region of oxide may be characterized by a thickness of less than or about 5 nm in embodiments, and may be characterized by a thickness of less than or about 4 nm, less than or about 3 nm, less than or about 2 nm, less than or about 1 nm, less than or about 9 Å, less than or about 8 Å, less than or about 7 Å, less than or about 6 Å, less than or about 5 Å, less than or about 4 Å, less than or about 3 Å, or less. By performing the operations on an oxide material characterized by a thickness less than or about a few nanometers, the effects of fluorosilicic acid may be reduced, which may reduce pattern deformation or collapse. Additionally, method 700 may maintain or limit the effect on substrate feature dimensions or substrate critical dimensions, which may be reduced by less than or about 5%, less than or about 4%, less than or about 3%, less than or about 2%, less than or about 1%, or may be substantially or essentially maintained by the method.
FIG. 9 shows exemplary operations in a method 900 according to embodiments of the present technology. Method 900 may include some or all of the operations, conditions, parameters, or results of method 400 or method 700 described previously. Method 900 may be performed on a residual oxide material as discussed above with regard to method 700 or method 400. For example, method 900 may include flowing a fluorine-containing precursor into a remote plasma region of a semiconductor processing chamber at operation 905. The precursor may be flowed while forming a plasma within the remote plasma region to generate plasma effluents of the fluorine-containing precursor at operation 910. The plasma effluents may be flowed into a processing region of the chamber at operation 915. A substrate may be housed within the processing region, and the substrate may be characterized by a high-aspect-ratio feature having a region of exposed oxide.
While the plasma effluents are being flowed into the processing region, a hydrogen-containing precursor may be flowed into the processing region at operation 920. The hydrogen-containing precursor may bypass the remote plasma region in embodiments. At operation 925 the precursors may be continuously flowed through the processing region for a period of time. At least a portion of the exposed oxide material may be removed during the precursor introduction at operation 930. During the removal, the relative humidity within the processing chamber may be maintained at greater than or about 50% as a threshold as described above.
Method 900 may also be effective at producing the benefits described previously in conditions where the relative humidity may not be capable of increase above a threshold value. Additionally, in conjunction with the increase in relative humidity and/or with an increase in fluorine-containing precursor flow rate, removal of oxide material may be performed over a period of time to further reduce the oxygen concentration at the substrate.
FIG. 10 shows a chart illustrating surface concentrations of elements in relation to elapsed time according to embodiments of the present technology. The fluorine-containing plasma effluents and the hydrogen-containing precursor were provided to the patterned substrate for a period of time as illustrated up to 400 seconds. The relative humidity during the operations was maintained between about 50% and about 65%. As illustrated, the method relatively maintained the fluorine concentration, while reducing the oxygen concentration in the substrate. The fluorine incorporation is shown by squares 1005, and the oxygen incorporation is shown by diamonds 1010. The chart additionally shows a reduction in residual oxide thickness with triangles 1015. As illustrated, the removal operations of method 900 may reduce the oxygen incorporation by at least or about 1%, and may reduce the oxygen incorporation by at least or about 2%, at least or about 3%, at least or about 4%, at least or about 5%, at least or about 6%, or more. The delivery of precursors and plasma effluents may be continued for at least or about 100 seconds in embodiments, and may be continued for at least or about 150 seconds, at least or about 200 seconds, at least or about 250 seconds, at least or about 300 seconds, at least or about 350 seconds, at least or about 400 seconds, at least or about 450 seconds, at least or about 500 seconds, or longer. As the time is increased, however, surface defects may be produced in the substrate, and may reduce surface uniformity on the substrate. Accordingly, in some embodiments the operations may be performed for less than or about 500 seconds.
The previously discussed methods may allow the removal of oxide material from a substrate while limiting the fluorine incorporation, and while maintaining critical dimensions of the substrate features, which may be high-aspect-ratio features. The operations performed may include one or more of increasing the relative humidity during the removal, increasing the fluorine-containing precursor flow rate during the removal, or continuing the removal for a period of time as discussed. Additional chamber operations may also be adjusted as discussed throughout the present disclosure. By utilizing the present methods and operations, high-aspect-ratio features may be cleaned or etched while not causing pattern collapse unlike wet etching, and while not increasing or while limiting impurity inclusion such as fluorine, unlike some conventional dry etching.
In the preceding description, for the purposes of explanation, numerous details have been set forth in order to provide an understanding of various embodiments of the present technology. It will be apparent to one skilled in the art, however, that certain embodiments may be practiced without some of these details, or with additional details.
Having disclosed several embodiments, it will be recognized by those of skill in the art that various modifications, alternative constructions, and equivalents may be used without departing from the spirit of the embodiments. Additionally, a number of well-known processes and elements have not been described in order to avoid unnecessarily obscuring the present technology. Accordingly, the above description should not be taken as limiting the scope of the technology. Additionally, methods or processes may be described as sequential or in steps, but it is to be understood that the operations may be performed concurrently, or in different orders than listed.
Where a range of values is provided, it is understood that each intervening value, to the smallest fraction of the unit of the lower limit, unless the context clearly dictates otherwise, between the upper and lower limits of that range is also specifically disclosed. Any narrower range between any stated values or unstated intervening values in a stated range and any other stated or intervening value in that stated range is encompassed. The upper and lower limits of those smaller ranges may independently be included or excluded in the range, and each range where either, neither, or both limits are included in the smaller ranges is also encompassed within the technology, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included.
As used herein and in the appended claims, the singular forms “a”, “an”, and “the” include plural references unless the context clearly dictates otherwise. Thus, for example, reference to “a precursor” includes a plurality of such precursors, and reference to “the layer” includes reference to one or more layers and equivalents thereof known to those skilled in the art, and so forth.
Also, the words “comprise(s)”, “comprising”, “contain(s)”, “containing”, “include(s)”, and “including”, when used in this specification and in the following claims, are intended to specify the presence of stated features, integers, components, or operations, but they do not preclude the presence or addition of one or more other features, integers, components, operations, acts, or groups.

## Claims

1. An etching method comprising:
flowing a fluorine-containing precursor into a remote plasma region of a semiconductor processing chamber;
forming a plasma within the remote plasma region to generate plasma effluents of the fluorine-containing precursor;
flowing the plasma effluents into a processing region of the semiconductor processing chamber, wherein the processing region houses a substrate comprising a region of exposed oxide;
providing a hydrogen-containing precursor to the processing region;
removing at least a portion of the exposed oxide while maintaining a relative humidity within the processing region below about 50%;
subsequent the removing at least a portion of the exposed oxide, increasing the relative humidity within the processing region to greater than or about 50%; and
removing an additional amount of the exposed oxide.

2. The etching method of claim 1, further comprising continuing to flow the plasma effluents into the processing region while increasing the relative humidity within the processing region.

3. The etching method of claim 2, wherein a flow rate of the plasma effluents is reduced while increasing the relative humidity within the processing region.

4. The etching method of claim 1, further comprising reducing a temperature of the substrate while increasing the relative humidity within the processing region.

5. The etching method of claim 4, wherein the temperature is reduced by at least about 5° C.

6. The etching method of claim 1, further comprising increasing a pressure within the processing chamber while increasing the relative humidity within the processing region.

7. The etching method of claim 6, wherein the pressure is increased by at least about 1 Torr.

8. The etching method of claim 1, wherein the relative humidity is increased above about 65%.

9. The etching method of claim 1, wherein after the additional amount of exposed oxide is removed, a concentration of fluorine in the substrate is below or about 5%.

10. The etching method of claim 1, wherein after the additional amount of exposed oxide is removed, a concentration of oxygen in the substrate is below or about 8%.

11. The etching method of claim 1, wherein the hydrogen-containing precursor bypasses the remote plasma region when provided to the processing region.

12. The etching method of claim 1, wherein the processing region is maintained plasma free during the removing operations.

13. The etching method of claim 1, wherein the relative humidity is increased incrementally by less than or about 20% per increment.

14. A cleaning method comprising:
flowing a fluorine-containing precursor into a remote plasma region of a semiconductor processing chamber while forming a plasma within the remote plasma region to generate plasma effluents of the fluorine-containing precursor;
flowing the plasma effluents into a processing region of the semiconductor processing chamber, wherein the processing region houses a substrate comprising a high-aspect-ratio feature having a region of exposed oxide;
while flowing the plasma effluents into the processing region, providing a hydrogen-containing precursor to the processing region;
removing at least a portion of the exposed oxide while maintaining a relative humidity within the processing region at greater than or about 50%;
subsequent the removing at least a portion of the exposed oxide, increasing a flow rate of the fluorine-containing precursor while maintaining the relative humidity within the processing region at greater than or about 50%; and
removing an additional amount of the exposed oxide.

15. The cleaning method of claim 14, wherein removing an additional amount of the exposed oxide lowers a concentration of oxygen by at least about 5%.

16. The cleaning method of claim 14, wherein the flow rate of the fluorine-containing precursor is increased by at least about 2 sccm.

17. The cleaning method of claim 14, wherein a thickness of the exposed region of oxide prior to the removal operations is less than or about 2 nm.

18. The cleaning method of claim 14, wherein a critical dimension of the high-aspect-ratio feature is reduced by less than or about 1%.

19. A removal method comprising:
flowing a fluorine-containing precursor into a remote plasma region of a semiconductor processing chamber while forming a plasma within the remote plasma region to generate plasma effluents of the fluorine-containing precursor;
flowing the plasma effluents into a processing region of the semiconductor processing chamber, wherein the processing region houses a substrate comprising a high-aspect-ratio feature having a region of exposed oxide;
while flowing the plasma effluents into the processing region, providing a hydrogen-containing precursor to the processing region;
continuing to flow the plasma effluents and the hydrogen-containing precursor into the processing region for at least about 200 seconds; and
removing at least a portion of the exposed oxide while maintaining a relative humidity within the processing region at greater than or about 50%.

20. The removal method of claim 19, wherein the removing operation reduces a concentration of oxygen within the substrate by at least about 3%.